Spinal Cord Injury (SCI): Condition Information

What is SCI?

SCI is usually associated with what is commonly called a broken neck or broken back. Generally speaking, SCI is damage to the spinal nerves, the body's central and most important nerve bundle, as a result of trauma to the backbone.

Most cases of SCI take place when trauma breaks and squeezes the vertebrae, or the bones of the back. This, in turn, damages the axons—the long nerve cell "wires" that pass through vertebrae, carrying signals between the brain and the rest of the body. The axons might be crushed or completely severed by this damage. Someone with injury to only a few axons might be able to recover completely from their injury. On the other hand, a person with damage to all axons will most likely be paralyzed in the areas below the injury.1

An SCI is described by its level, type, and severity. The level of injury for a person with SCI is the lowest point on the spinal cord below which sensory feeling and motor movement diminish or disappear.

The level is denoted by the letter-and-number name of the vertebra at the injury site (such as C3, T2, or L4).

There are seven cervical vertebrae (C1 through C7), which are in the neck.

There are 12 thoracic vertebrae (T1 through T12), which are located in the upper back. There are five lumbar vertebrae (L1 through L5), which are found in the lower back.

Below those are five sacral vertebrae, which are fused to form the sacrum. Finally, there are the four vertebrae of the coccyx, or tailbone.1

There are two broad types of SCI, each comprising a number of different levels:

Tetraplegia (formerly called quadriplegia) generally describes the condition of a person with an SCI that is at a level anywhere from the C1 vertebra down to the T1. These individuals can experience a loss of sensation, function, or movement in their head, neck, shoulders, arms, hands, upper chest, pelvic organs, and legs.

Paraplegia is the general term describing the condition of people who have lost feeling in or are not able to move the lower parts of their body. The body parts that may be affected are the chest, stomach, hips, legs, and feet. The state of an individual with an SCI level from the T2 vertebra to the S5 can usually be called paraplegic.2

In addition, there are two degrees of SCI severity:

Complete injury is the situation when the injury is so severe that almost all feeling (sensory function) and all ability to control movement (motor function) are lost below the area of the SCI.

Incomplete injury occurs when there is some sensory or motor function below the damaged area on the spine. There are many degrees of incomplete injury. 1

The closer the spinal injury is to the skull, the more extensive is the curtailment of the body's ability to move and feel. If the lesion is low on the spine, say, in the sacral area, it is likely that there will be a lack of feeling and movement in the thighs and lower parts of the legs, the feet, most of the external genital organs, and the anal area. But the person will be able to breathe freely and move his head, neck, arms, and hands. By contrast, someone with a broken neck may be almost completely incapacitated, even to the extent of requiring breathing assistance.3